Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
T = [[] for i in range(H)]
b = 0
for i in range(H):
    T[i] = list(input())
    for j in range(W):
        if T[i][j] == '#':
            b += 1

que = [(0, 0, 1)]
while que:
    x, y, k = que.pop(0)
    if x == H - 1 and y == W - 1:
        print(H * W - b - k)
        exit()

    for dx, dy in [(0, 1), (1, 0), (-1, 0), (0, -1)]:
        nx, ny = x + dx, y + dy
        if 0 <= nx < H and 0 <= ny < W and T[nx][ny] == '.':
            T[nx][ny] = '#'
            que.append((nx, ny, k + 1))
print(-1)